This application claims the benefit of Korean Application No. 2000-9457 filed Feb. 25, 2000, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a beam index type cathode ray tube, which includes a plurality of deflection units, a plurality of electron guns and a screen divided into a plurality of parts in order to realize high quality images.
2. Description of the Related Art
A beam index type cathode ray tube is designed for reducing problems associated with general cathode ray tubes, in which sensed index signals, which are excited by an electron beam emitted by an electron gun, are synchronized with color signals and reach desired positions to allow phosphors to emit lights, thereby realizing images.
The beam index type cathode ray tube has the advantages that mis-landing of electron beams due to doming of a shadow mask does not occur since the shadow mask is not employed as a color selection apparatus, and that misconvergence due to crossing of red R, green G and blue B electron beams is prevented since color images are realized by a single electron gun.
However, a problem of the beam index type cathode ray tube is that the electron beam should be limited to an optimum size in order to prevent the electron beam from colliding against phosphors other than a desired single color of phosphor and landing the electron beam on a peripheral part of a screen at an incline should be avoided.
Further, the beam index type, as described above, selects landing positions of the electron beam by sensing index signals so that a persistence time of index phosphors becomes an important factor in order to distinguish the index signals according to the synchronization of the color signals.
If the persistence time of the index phosphors becomes too long, the index signals are not distinguished and accordingly, assignment of the color signals becomes impossible. Therefore, in the related art, a beam index type cathode ray tube employs extremely short persistence time index phosphors.
In order to realize high resolution where the beam index type cathode ray tube is applied to HDTVs or digital TVs, the persistence time of the index phosphors should be much shorter than that of the existing index fluorescent substances, since a high frequency deflection velocity (approximately 30 kHz or more) of the HDTV or digital TV systems is faster than a high frequency deflection velocity (approximately 15.75 kHz) of the existing NTSC or PAL systems.
However, index phosphors satisfying the above condition have not been suggested specifically, so that the high resolution images can not be realized by the beam index type cathode ray tube.
Japanese laid-open publication No. 62-176036 discloses a beam index type color picture tube to resolve the above problems by changing a geometrical shape of the beam index type cathode ray tube.
The color picture tube includes a faceplate with a screen that is divided into a plurality of parts, necks connected with the faceplate through a funnel, and a plurality of electron guns fitted within the necks and deflecting yokes.
The color picture tube is structured to realize images by radiating electron beams which are emitted by the plurality of electron guns onto divided small regions of a screen to reduce a distance between the electron guns and the screen, that is, the whole length of the tube, wherein a size of the electron beams which collide against phosphors of the screen becomes reduced, so that the problems of collision of any colors of phosphors other than a desired color phosphor and the inclination of the electron beams may be resolved.
However, the above color picture tube has a disadvantage that the resolution over the whole screen is not maximized over a certain limit since only a single detector is mounted to sense the index light beams.
A problem results from the sequential radiation of electron beams with relation to the divided screen. For example, if the screen is divided into four areas and the radiation of the electron beams is carried out sequentially as above, it is difficult to maintain a deflection frequency above 15.75 kHz due to the persistence of the phosphors, and accordingly, the deflection frequency over the whole screen is limited to 15.75 kHz. In other words, the resolution of the color picture tube is achieved at about 500xc3x97500 as in the existing broadcasting systems such as NTSC.
Therefore, an object of present invention is to resolve the above disadvantages and problems of the related art and to provide a beam index type cathode ray tube which is implemented as a high resolution display system by maximizing resolution with relation to a whole screen, where a screen area is divided into a plurality of areas and provided with electron guns corresponding to the divided areas to realize images.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention.
In order to achieve the above and other objects of the present invention, a beam index type cathode ray tube includes a tube of which inner atmosphere is maintained in a vacuum state. A screen having phosphor stripes and index stripes is formed at one side of an inner surface of the tube and a plurality of electron guns are mounted in the tube facing the screen part. A plurality of deflection units which deflect electron beams which are radiated from the electron guns to the screen, are mounted on the tube corresponding to the electron guns. A plurality of detectors mounted on the tube corresponding to the electron guns sense lights emitted from the index stripes.